A. Field of the Invention
The present invention relates generally to configurable computing devices and, more particularly, to hot-swappable cards that can be inserted and removed from the computing device while the device continues to operate.
B. Description of Related Art
Certain computing devices include the ability for the end-user to add and remove hardware components to/from the computing device. For example, a graphics or sound card may be added to a personal computer to increase the performance of the computer. A basic implementation of such a dynamic card insertion requires that the user turn off the computing device before inserting the new card. The computing device then detects, the next time it is turned on, the new hardware card. In this manner, the functionality of the core computing device can be extended by adding an appropriate hardware card.
Some add-on hardware components are xe2x80x9chot-swappablexe2x80x9d (also called xe2x80x9clive insertion/removalxe2x80x9d) meaning that the user does not have to reset the computing device when inserting or removing the hardware component. Instead, the user simply inserts or removes the hardware component while the computing device is operating, and the computing device dynamically recognizes and begins to communicate with the new hardware component. In this manner, the new component can be inserted and removed from the computing device without interruption of the device.
Hot-swappable add-on components are particularly desirable in critical computing devices that should not be taken off-line. For example, high performance network routers may route traffic through a network for many thousands of users. A router is a device that controls the flow of data packets in a network. It is desirable that these routers operate continuously and without interruption. Accordingly, when inserting add-on components to a high-performance router, it is desirable that the add-on components be hot-swappable.
There are a number of problems that may occur when designing a hot-swappable system for sensitive, high-performance systems. One problem is power disruptions. Inserting a hardware component, such as a circuit board, into an operational system can cause power disruptions due to the sudden increase in load presented to the power supply and the finite response time of that power supply. This is especially true when high capacitance values are used on the circuit board being inserted. This results in an in-rush current which can starve neighboring circuits, potentially causing the logic on these circuits to reset or experience errors.
In addition to power disruptions, software disruptions can occur when inserting and removing a circuit board. In particular, upon removal of a circuit board, the software controlling the system may try to access the board and fail to get a response, thus causing a fatal error. A variation on this problem can occur on insertion if the software tries to access the circuit board before it is fully inserted and stable in the system.
Thus, there is a need in the art to be able to reliably implement hot-swappable components in a high-performance computing device such as a router.
Systems and methods consistent with the present invention address this and other need to effectively implement hot-swappable interface cards in a router.
In accordance with the purpose of the invention as embodied and broadly described herein, a first aspect of the present invention is directed to a network device including slots for hot-swappable physical interface cards. The network device includes an interface designed to receive the physical interface cards, a plurality of power supply lines, and an on/off power control circuit connected to the plurality of power supply lines. Finally, a controller is connected to the on/off power control circuit. The controller, in response to detecting the presence of the physical interface card in the interface, instructs the on/off power control circuit to turn on the power supply lines by ramping the power supplied to each one of the sequentially turned on power supply lines.
A second aspect of the present invention is directed to a hot-swappable physical interface card designed to be inserted into a network device. An interface in the physical interface card connects the physical interface card to the network device and includes a number of connections. These connections include power supply lines through which power is received from the network device, a high-speed data bus for transmitting and receiving packets of information from the network device, and a control bus. The network device sequentially activates the power supply lines and ramps the power supplied to each one of the sequentially activated power supply lines in response to the network device detecting insertion of the physical interface card.
Additional aspects of the present invention are directed to methods for inserting and removing interface cards from the network device.